The invention relates to a filtration device with a housing and with at least one filter module which is inserted into the housing and which has two end plates and several filter elements located in between, the housing having openings for supplying the unfiltered material and for removing the filtered material.
In filtration, filter presses to hold filter frames for kieselguhr filtration or to hold filter frames and the filter beds which are located in between are known. In the case of filter presses for holding filter beds they generally do not have a jacket which screens the filter beds from the exterior space. Rather the unfiltered material space and the filtered material space are separated from one another and from the environment only by pressing of the filter beds and the filter frames which lie between them. But these filter frames cause up to 50% of the production costs of a corresponding apparatus. In addition, as a result of the lack of screening from the environment and the associated continually necessary monitoring, automation of the filtration process is possible only to a very limited degree.
A survey of the art can be found in Horst Gasper Handbook of Industrial Solid-Liquid Filtration, Huethig-Verlag 1990, p. 166ff.
In these filtration devices automation in the changing of filter elements is not possible, so that the filter elements must be inserted individually into the filter by hand before filtration and removed from the filter after filtration. However this causes high costs due to the personnel required and due to shutdown of the filtration line.
For special applications it is necessary for economic reasons that the filter can be flushed clean by reversing the flow after filtration. But this is impossible in many filtration units on the market, or the special construction of the filters causes very high additional costs.
DE 3520171 A1 discloses a filter press of horizontal design which has a protective jacket which surrounds the filter packet. The filter press requires filter frames and filter plates for sealing between the filter elements since they form the unfiltered material and filtered material spaces. Since sealing cannot take place directly between the individual filter elements, this causes much higher investment for the filter press, at the same time the filter frame and filter plates must be made very complex. Furthermore, the segmenting and the associated necessary manual outfitting of the filter press with individual filter elements cause high costs when the filter elements are changed. Filtration in these known filtration means takes place perpendicularly to the surface of the plate-shaped elements. The end plates, as in the filter means described below, form only one wall of the unfiltered material space or of the filtered material space.
A similar filter type in a vertical design is known under the product name xe2x80x9cradium filterxe2x80x9d. This type of filter has round filter frames which are assembled externally into a filter module with a disk in between. These packages are then lifted into a corresponding housing. These filter frames during filtration form spaces for unfiltered material and for filtered material by distributing the flow. In particular the manual separation between the filter frame and the filter beds after operation of the filtration means causes very high costs and is possible only with great burdens for the personnel, for example in the case of filtration of toxic fluids or fluids with high vapor pressures, as is the case in many organic solvents. Furthermore, the precisely formed filter frames cause a high proportion of the investment costs to be borne for this filter.
DE 3906815 A1 and DE 3906816 C3 describe a filter plate and a bed filter with a space which encompasses the filter beds and which is designed to prevent environmental contamination during a leak. For operation of the bed filter a plurality of the filter plates described in DE 3906815 A1 are necessary. This increases the amount of investment for the filter device. Furthermore, due to the plurality of sealing elements between the filter plates safety during filtration is only conditionally greater than in other known filter devices. Changing of the filter beds is likewise as complex as in conventional filter devices.
A filtration device with a closed outside jacket is described on the other hand in DE 3234560 C2. In any case, for operation exactly as in the aforementioned filtration means filter frames are necessary which are called filter carriers. Here especially the manual separation of the filter carriers from the filter packings is complicated. As described in DE 3403738 C2, production of filter packings is moreover very complex since each filter body must be formed individually.
The object of the invention is to devise a filtration device for deep-bed filtration which is can be more easily handled such that replacement of the filter module or modules is easily possible and in which the modules can be easily disposed of, furthermore there being possibility of backflushing.
This object is achieved with a filtration device in which the filter module has filter elements of deep-bed filter material which are stacked on top of one another and which have at least one inner structure formed by an opening, the boundary surface of the opening formed by the deep-bed filter material forming a flow surface for the filtered material or the unfiltered material, and at least one end plate having at least one entry and/or discharge opening.
Sheet filters and filter beds consist of deep-bed filter materials which are defined as those materials which are porous and through which flow can take place, i.e. in which convective transport of substances through the materials is possible. Deep-bed material can have organic and/or inorganic, fibrous and/or grainy substances. Raw materials for the deep-bed filter material can be for example cellulose, plastic fibers, kieselguhr, perlites or metal oxides. Here kieselguhrs and perlites can be added to the filter beds to increase the internal surface and thus the prefilt volume. Furthermore, in the cavities components of the fluid to be treated can be retained by blocking action and/or absorption/adsorption. Examples of materials which can be used for deep-bed filter needs include paper, cardboard, filter beds, membranes, porous ceramic materials, metal or polymer fabric, nonwovens, and sintered materials, for example, of metals, metal oxides, glass or polymers.
Based on their internal structure, flow through the filter element which is preferably a filter disk can take place parallel to the disk plane, incident flow being possible both via the outside peripheral surface which acts likewise as a flow surface so that the filtered material collects in the corresponding openings of the internal structure and also via the flow surfaces formed by the internal structure. In this way the filter disks can be stacked on top of one another without holding frames or the like so that a filter module can be produced from a single material. This filter module can be assembled outside of the filtration device and can be inserted as a unit into it. When the filter material must be replaced, the entire module can be removed and disposed of as a unit without additional effort, as in the prior art, for example, disassembling the module in order to remove the holding frame. This saves time and personnel.
Preferably the sum of all flow surfaces of a filter element, which is also to be understood as both the outer flow surfaces and also the flow surfaces located within the filter element, is larger than the sum of the outer peripheral surface of an extremely small convex body which jackets the filter element and the outer peripheral surface of an extremely large convex body which is inscribed into any opening of the filter element. Convex bodies are for example spheres, ellipsoids, cylinders, cones, angles, tetrahedrons or cuboids and are described in the Small Mathematical Encyclopedia, VEB Bibliographisches Institut, Leipzig 1979, p. 625.
Preferably in filter elements we distinguish between openings of the first and second type which are not connected to one another. The filter elements can be stacked on top of one another such that only openings of the same type are connected to one another and form channels for filtered material and unfiltered material within the filter module.
Preferably at least one filter element of the filter module has an opening which extends to the edge of the filter element and which produces a connection to the inner structure of the filter elements. When for example an incident flow from the outside is to be effected, the filter material is exposed to flow not only via the peripheral surface, but the unfiltered material can also penetrate into the interior of the filter module via the connection openings which extend as far as the edge of the filter element, so that the flow surfaces formed by the inner structure can be used without the need for corresponding feed via specially formed end plates.
Preferably the filter disks have at least one collection opening to form a filtered material collection channel in the filter module, in this case there being a corresponding discharge opening in one of the end plates. In the reverse mode of operation the unfiltered material can be delivered via this collection opening.
Furthermore, the openings and/or connection openings can have stiffening bridges in order to increase stability. Identical or different types of filter elements or filter disks can be stacked on top of one another to form a filter module.
The filter elements can preferably be made by their inner structure such that only one type of filter element is necessary in order to build an effective filtration module. The filter elements can all be stacked on top of one another in the same way. If however the inner structure makes it necessary, the individual filter elements can be twisted each against one another.
Due to the filtered material and unfiltered material channels within the filter module at least one of the end plates must have a corresponding feed and discharge opening. In the simplest case the upper end plate can be completely closed and the lower end plate has simply one discharge opening for the filtered material. This applies to the case of outside incident flow of the filter module.
When the filter module is to be exposed to incident flow from the inside, the unfiltered material is supplied via this discharge opening. At least one end plate can also be made for distributing the unfiltered material into the unfiltered material channels of the filter module and/or collecting the filtered material. Preferably in this case at least one of the end plates has the corresponding distributor channels which are connected to the corresponding openings of the first type and/or second type. The distributor channels form a communicating channel system which is connected only to the openings of one type so that no mixing of filtered material and unfiltered material can occur. The openings of the respective other type are either covered by the end plate or are connected to their own distributor system in the end plate. Which configuration of the end plate is chosen depends on the embodiment of the filter elements and the desired operating mode.
The filter elements can lie directly on top of one another, it being possible to cement or bond the filter elements to one another.
Basically the filter module as claimed in the invention requires no intermediate layers. But it can be a good idea for different reasons to use intermediate layers, films, filter disks without openings or even metal plates; especially high quality steel plates can be used. Especially when metal plates are used are they arranged at greater distances in the filter module in order not to adversely effect the disposal advantages of the module.
Intermediate layers can be used to increase the strength of the filter module when due to a complex inner structure the stability of the filter elements suffers and they tend to radial deformation. Bulging can occur when the filter module is backflushed, if this is not prevented by the intermediate layers.
Furthermore, intermediate layers provide for segmenting of the filter module, facilitating installation, because the module can be composed of several parts which can be easily handled. Instead of speaking of segmenting of a filter module, it is also possible to speak of several filter modules which are stacked on top of one another, and in this case the intermediate plates could then be called end plates.
When the intermediate layers consist of deflection-resistant material, such as for example high quality steel with the corresponding thickness, for example 3 mm, these intermediate plates also contribute to greater uniformity of contact pressure.
Preferably the filter module is located perpendicularly in the housing, by which installation and disassembly are facilitated. Moreover the vertical arrangement is advantageous for good venting.
Advantageously one of the two end plates, especially the upper end plate, is movably supported so that the swelling capacity and thus the expansion of the filter element stack can be considered. In the housing there can be a pressing device which preferably engages the movably supported end plate. This pressing device can act from the top and/or from the bottom on the filter module.
When several filter modules in the filtration device are located on top of one another and/or next to one another, there can be a common pressing device or, for each individual filter module, its own pressing device.
According to another embodiment there is at least one fixing element which fixes the filter discs in their relative position to one another at least during installation. Depending on the type of configuration of the inner structure of the filter elements the latter must be stacked on top of one another according to a certain pattern so that no short circuit occurs between the channels for the filtered material and unfiltered material. These fixing elements can interact with the recesses on the edge of the disk or also in the interior of the filter module so that the location of the filter disks to one another is explicitly fixed.
The fixing element is preferably a component of a holding means which is connected to at least one end plate. Preferably the holding means has two rods via which the two end plates can be connected to one another, the rods fitting into outside grooves of the filter module which are formed by the recesses of the filter elements. It is possible to remove the entire module from the filtration device by this holding means.
Within the filter module there can be at least one retention means. In this way further filtration can take place to again further increase the purity of the filtered fluid or to additionally reliably sterilize the fluid with membrane filtration. Here it is important that the length of the retention means which can preferably be a cartridge filter, with or without pleating, or a screen filter, be shorter than the minimum length of the filter module with maximum pressing, so that the cartridge filter is not flattened. Preferably the mobility of the end plates will be limited to prevent damage.
The retention means can be detachably fastened to one of the two end plates.
Sample embodiments of the invention are detailed below using the drawings.